There are number of materials that have value as fuels, but are in a form that is intractable for use as a fuel in terms of handling. For example, coal mining, processing, and handling produces millions of tons of coal fines that cannot be readily burned as fuel due to issues with handling and transport. Coal fines may be made into usable fuel by combining and compacting with other materials such as a starch/oil emulsion (U.S. Pat. No. 1,851,689), starch and molasses (U.S. Pat. No. 5,009,671), asphaltic binder material (U.S. Pat. No. 823,025), bitumen binders (U.S. Pat. No. 3,966,427), or liquefied biomass (U.S. Pat. No. 5,916,826). Extrusion and pelletizing processes have been used to make readily transportable and easily handled fuel pellets containing coal fines.
There are additional materials that have fuel value, but are powdery or granular and thus not amenable to fuel use. These materials could be used as fuel if they could be made into a convenient, easily handled product. This includes biomass materials such as wood dust, milled biomass, and co-products from processes that use lignocellulosic biomass.
In a cellulosic ethanol process which makes use of lignocellulosic biomass as a carbon source for fermentation, whole stillage from a distillation column (beer column) is typically separated into solids (wetcake or filter cake) and liquid (thin stillage) fractions. The thin stillage is passed through evaporators producing a syrup. The filter cake and syrup are co-products of the cellulosic ethanol process. A syrup with at least about 40% solids may be burned as disclosed in U.S.20120102823, thereby providing energy. The filter cake may also be burned to provide energy.
There remains a need for compositions of materials that are convenient to handle and useful as burnable fuels, that are made from materials that are otherwise difficult to use as fuels.